This invention relates in general to injection moulding for plastic materials and, more specifically, to an injector for injection moulding of plastic materials.
Traditionally said injectors comprise a body with a passage for running hot plastic material into the mould, a pin axially movable in the body for controlling said passage and a linear actuator for controlling displacement of the pin between an advanced closed position of said passage and a retracted open position of said passage.
In injection moulding apparatuses, a fundamental control parameter is the pressure inside the mould following injection of the plastic material. Traditionally, the pressure is directly measured in the mould, by means of specific sensors or transducers applied therein. This arrangement, in addition to not being very flexible and being relatively expensive, presents the drawback of not ensuring the required pressure measuring accuracy in all conditions.
The object of this invention is to provide a new and unique solution to overcome said drawback.
According to this invention, this object is attained by a injector for plastic material injection moulding of the type above, the primary feature of which resides in that it is provided with a sensor for measuring the pressure inside the mould which is operatively associated to said pin.
According to a preferred form of embodiment of the invention, the pressure sensor is operated by the movement of the pin to said retracted position, conveniently by means of a mobile slider arranged on the extension of said pin.
Thanks to this idea, the application of pressure sensors in the injection mould is no longer necessary. Furthermore, the arrangement according to this invention of the pressure sensor allows the application to existing injectors.